Performance
· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.Performance-focused optimization plan with CWV assessment, top offenders, and time estimates
First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.
2.51 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
4.31 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
224 ms
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.000
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
3.00 s
Time to Interactive Time to Interactive — how long until the page is fully interactive and responds to user input. Under 3.8s is good.
9.37 s
Page Load Progression
375 ms
750 ms
1.1 s 1.5 s 1.9 s 2.2 s 2.6 s 3.0 sDThird-Party ImpactAction100% third-party, 0 ms blockingFIX
DJS BundlesAction5 scripts, 349 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://www.aboutcookies.org/assets/js/index.js?v=20260418003154 | 299 KB | 224 KB (75%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-463CHWS42G&cx=c>m=4e64h1 | 144 KB | 63 KB (44%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-WQZFSCP | 133 KB | 61 KB (46%) | ✓ | 3rd |
| https://az416426.vo.msecnd.net/scripts/a/ai.0.js | 22 KB | — | ✓ | 3rd |
| https://www.google-analytics.com/analytics.js | 21 KB | — | ✓ | 3rd |
Consider code splitting or tree shaking to reduce unused code.
This bundle has high unused code — code-split or tree-shake to ship only what executes.
Source: web.dev / Lighthouse coverage
Consider code splitting or tree shaking to reduce unused code.
This bundle has high unused code — code-split or tree-shake to ship only what executes.
Source: web.dev / Lighthouse coverage
Consider code splitting or tree shaking to reduce unused code.
This bundle has high unused code — code-split or tree-shake to ship only what executes.
Source: web.dev / Lighthouse coverage
DPage Weight InventoryAction26 resources · 1.3 MB · 349 KB savings availableFIX
~348.6 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 26 resources | 1.3 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
BPage Weight Budget1.3 MB transferred, 26 requestsREVIEW
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
JavaScript bundle is large — code-split routes and lazy-load off-screen components to defer.
Source: web.dev
CImage OptimizationAction7 images, 0 KB saveableREVIEW
Set explicit width and height to prevent CLS.
Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.
Source: web.dev / Core Web Vitals
Set explicit width and height to prevent CLS.
Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.
Source: web.dev / Core Web Vitals
Set explicit width and height to prevent CLS.
Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.
Source: web.dev / Core Web Vitals
Set explicit width and height to prevent CLS.
Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.
Source: web.dev / Core Web Vitals
CJS Execution CostAction1475ms total JS executionREVIEW
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| Unattributable | 443ms | 6ms | 0ms | 3rd |
| https://www.aboutcookies.org/ | 332ms | 85ms | 7ms | 3rd |
| https://www.aboutcookies.org/assets/js/index.js?v=20260418003154 | 249ms | 144ms | 83ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-463CHWS42G&cx=c>m=4e64h1 | 194ms | 162ms | 31ms | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-WQZFSCP | 177ms | 144ms | 32ms | 3rd |
| https://az416426.vo.msecnd.net/scripts/a/ai.0.js | 80ms | 48ms | 26ms | 3rd |
A+Text CompressionAll text resources are compressedPASS
A+Font Loading4 fonts (146 KB)PASS
Web fonts
4
146 KB total
Render-blocking
0
of 4
Dominant font-display
swap
Most common across fonts
Font loading timeline
Optimization checklist
- Preload critical fonts (priority=high)
- Use woff2 format for all fonts
- Set font-display to swap, optional, or fallback
- Subset large fonts (≤100 KB each)
A+Resource CachingAll resources properly cachedPASS
A+Critical Rendering PathNo render-blocking resourcesPASS
A+Resource Hints5 hints, 0 missing preconnectsPASS
Current Resource Hints
5 resource hints configured
A+Render-Blocking ResourcesNo render-blocking resources detectedPASS
A+Third-Party ResourcesNo third-party resources detectedPASS
A+Green HostingWhether the site is served from green-energy infrastructurePASS
Green Hosting
This site is hosted on green energy infrastructure
Provider: Cloudflare
Network Waterfall26 requests over 995msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
Unattributable Unattributable | Other | 443ms | 0 KB | — | £7/mo | Costly |
www.aboutcookies.org www.aboutcookies.org | Other | 332ms | 32 KB | — | £5/mo | Costly |
www.aboutcookies.org www.aboutcookies.org | Other | 249ms | 299 KB | 75% | £4/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 194ms | 144 KB | 44% | £3/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 177ms | 133 KB | 46% | £3/mo | Optional |
az416426.vo.msecnd.net az416426.vo.msecnd.net | Other | 80ms | 22 KB | — | £1/mo | Optional |
These scripts may cost more than they're worth
- Unattributable adds 443ms and costs ~£7/month
- www.aboutcookies.org adds 332ms and costs ~£5/month
- www.aboutcookies.org adds 249ms and costs ~£4/month
100% of JavaScript execution time is spent on third-party scripts. Consider auditing which scripts are essential.
When third-party JS execution time exceeds your own, performance gains from frontend work are capped by code you don't own.
Learn more ▾ ▴
Every millisecond of third-party JS competes with your own for main-thread time. If their share is bigger than yours, optimization on your code base barely moves the needle. Audit, defer, or remove third-parties before further frontend optimization. Use Lighthouse's third-party audit to identify the worst offenders.
Source: web.dev
Unattributable takes 443ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
www.aboutcookies.org takes 332ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
www.aboutcookies.org takes 249ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
75% of www.aboutcookies.org's code is unused. The script may be loading features you don't use.
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev